# How to calculate force exerted by ground

In summary: For the first phase you have (assuming that the rocket started at rest)v = u + atv = 175 m/su = 0t = 0.04 sa = ?Rearranginga = (v - u)/ta = (175 - 0)/0.04a = 4375 m/s^2In summary, the force exerted by the ground on the rocket can be calculated by breaking the problem into different phases and applying the equations of motion to each phase separately. For the impact phase, with a duration of 0.04 seconds and a velocity of 175 m/s, the acceleration can be calculated as 4375 m/s^

## Homework Statement

Force exerted by the ground on the rocket

Mass of the Rocket = 1500kg
Duration of landing impact = 0.04 s
Velocity at time of impact = 175 m/s
Distance traveled = 30km
Time taken to complete journey = 6 minutes
Acceleration due to gravity = 9.8 m/s^2

## Homework Equations

Can't find the one I am looking for

## The Attempt at a Solution

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Not going to lie I've attempted it but i don't know what formula to use and I've done all the questions before except one, please may someone tell me the equation I am supposed to use?

So the problem is to find the force exerted by the ground on the rocket? You are given 0.04 s as the duration of landing impact. And you are given the velocity at the start of the impact is 175 m/s. So you have three things that you know: initial velocity, final velocity and time. What can you find from knowing those three parameters?

Force exerted by the ground on the rocket
It is unclear what is being asked for. Is it the average force during impact, or the average force over the duration of flight plus impact?
Please post the original question word for word.

Calculate the force exerted by the ground on the rocket (use correct units)

Mass of the Rocket = 1500kg
Duration of landing impact = 0.04 s
Velocity at time of impact = 175 m/s
Distance traveled = 30km
Time taken to complete journey = 6 minutes
Acceleration due to gravity = 9.8 m/s2

I got:
Final velocity = 175 m/s
Initial velocity = u=v-at → u=175-(9.8*360) = -3353

Force exerted by the ground on the rocket (N)

F = mass*acceleration
Acceleration = change in velocity/time = Final Vel.-Initial Vel./0.04 = 175-(-3353)/0.04=84000m/s2
F = 1500*84000 = 126000000 N

Initial velocity = u=v-at → u=175-(9.8*360) = -3353
Not sure what you think you are calculating there. You seem to be saying that at the start of the 6 minutes the rocket was going vertically upward with speed u, that for the remainder of the 6 minutes it was in free fall, so that at the end of the 6 minutes it was falling at 175 m/s. None of that sounds right to me. For a start, to finish at ground level it would have had to start some kilometres below ground.

You description of the question in post #4 still does not read like a complete statement. Is there nothing before that? I would expect it to start with some text like "A rocket is fired from the ground..."
And I still cannot tell whether it is asking for the average force during impact or the average force over the whole trajectory.

AdeptDz... The equations of motion you are using only work for constant acceleration. In this problem the acceleration of the rocket in flight is not the same as when it hits the ground.

So you have to break the problem into different phases and apply the equations to each phase separately.

This means that the "Initial velocity" you need to plug into the equation is the initial velocity of that PHASE which is not necessarily the initial velocity at the start of the problem.

This question asks about the impact force with the ground so the relevant initial velocity is the velocity with which it hits the ground not the launch velocity.

## 1. How do I calculate the force exerted by the ground on an object?

The force exerted by the ground on an object can be calculated by using the formula F = m x g, where F is the force, m is the mass of the object, and g is the acceleration due to gravity (9.8 m/s^2).

## 2. What is the unit of measurement for force?

The unit of measurement for force is Newtons (N). This unit is named after Sir Isaac Newton, who first described the laws of motion.

## 3. Can the force exerted by the ground on an object be negative?

Yes, the force exerted by the ground on an object can be negative if the object is moving in the opposite direction of the force. This is known as a resistive force.

## 4. How does the surface of the ground affect the force exerted on an object?

The surface of the ground can affect the force exerted on an object because different surfaces have different levels of friction. Rough surfaces will exert more force on an object compared to smooth surfaces.

## 5. What factors can affect the force exerted by the ground on an object?

The force exerted by the ground on an object can be affected by the mass of the object, the surface it is on, and the acceleration due to gravity. Other factors such as air resistance and the angle of the surface can also affect the force exerted.

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